The present invention is a needle-less injection device for the injection of liquids into the body of a patient, particularly in the oral region.
At present, the most common way of delivering local anesthetics is with the use of needles. Unfortunately, for many patients, the most unpleasant moment of a dental visit is the needle prick. Furthermore, the use of needles carries the risk of needlestick injuries and cross-contamination. We have therefore aimed to design an injection device that does not require needles. Although several needle-less devices are currently available, many of them have several disadvantages. They are rather large and heavy due to their complicated loading mechanisms. A frequently used product on the market has a weight of about 590 g, is 28 cm long and costs approximately US$1700. In addition, the large devices pose psychological disadvantages for the patient.
The present invention aims to make an improved injection device available. With the features of our claim, this aim has been achieved.
WO-A-96/36381 describes a injection device for high pressure injection of fluids or particle-containing fluids. This injection device has a piston in a pressure chamber that opens into an injection orifice. The fluid-driving force is produced by an elastic stroke on the piston that accelerates to the stop on the opposing side. The volume of the pressure chamber is bigger than the extruded fluid volume.
Other needle-less injection devices include those described by WO-A-94/07554, WO-A-95/03844, WO-A-96/24398, WO-A-95/27523; WO-A-95/16481, WO-A-97/13536, EP-A-370 571, EP-A-286 798, EP-A-27,6 158 or DE-A-33 28 173.
The invention is based on the idea that the needle-less injection device has a coupling on the opposite side of the nozzle, similar to those found in conventional dental devices such as drive drills, burr polishers etc. This device can be activated by connection to the coupling of any usual dental unit. A rotating-element that is meshed to a gearwheel and another axial movable rotating-element is provided on the opposite side of the nozzle . These rotating-elements produce tension in the spring-element.
The needle-less injecting device 2 has the advantages of having no complicated loading mechanisms to produce tension in the spring-element, and that the device itself can be built comparably small and simple. It is made of few parts, requires little or no maintenance, and can be sterilized easily. Customary carpules containing anesthetics can also be used. Compared to needle injection devices, there is no danger of needle fracture and the risk of allergy or toxic reactions can be minimallsed through the reduction of the quantity of administered anesthetics. Another advantage of the needle-less technique is that the patient does not have to be afraid of pain, During the injection the patient only feels a short tap. Thereby, the acceptance for this method of injection will rise, and better treatment success can be expected.